This research is an investigation of the biosynthesis of estrogens and other steroid hormones, and the interrelationships between human development and steroid hormones. It aims also to develop useful biochemical and analytical methods of clinical applicability. Our immediate objectives are: (1) to elucidate the steric, kinetic, and electronic mechanisms of aromatization and lyase reaction by human steroid hormone synthesizing systems, (2) to elucidate pathway(s) through which hydroxylated steroid hormones are formed, (3) to isolate natural steroids and their conjugates and study the mode of conjugation and excretion, (4) to elucidate steroids and their conjugates and study the mode of conjugation and excretion, (4) to elucidate steroid conformations, (5) to purify and characterize aromatase, and (6) to develop active-site directed affinity labeling steroids as enzyme tracer and as specific endocrine inhibitors in order to further our understanding of endocrine processes at the molecular level. The methods are synthesis of steroids with and without deuterium, tritium, carbon-13, carbon-14 and oxygen-18 labels at stereoselective and/or regiospecific positions, conformational analysis of isotopes, incubations with various enzyme preparations and tissues of combinations of regio- and stereoselectively labeled steroids, and analyses of the products, and the kinetic and dynamic intermediates. A neutral resin, steady state distribution machine, chromatographies, nmr and mass spectrometry are used for the isolation and characterization of steroids and their conjugates.